<form method="post" action="1-111.php">
    计算器<input type="text" name="s1" size="5" value=" "/>
    <select  name="fuhao">
        <option value="+">+</option>
        <option value="-">-</option>
        <option value="*">*</option>
        <option value="/">/</option>
    </select>
    <input type="text" name="s2" size="5" value=" "/>
    <input type="submit" name="dengyu" size="5" value="="/>
    <input type="text" name="sum" size="5" value=""/>
</form>